In fossil fuel burners it is well known that the addition of water vapor enhances the combustion efficiency. Introduction of water vapor may be solely by positive pressure, U.S. Pat. No. 3,724,429; negative pressure (vacuum), U.S. Pat. No. 3,107,657; or both positive and negative pressure, U.S. Pat. No. 3,862,819. In this last-mentioned patent, the concept of water vapor introduced into a combustion chamber is applied to central heating units, such as oil heaters. This patent provides a fuel catalyzer which has a first conduit from the high pressure side of the fan associated with the oil burner to a position below a reservoir of water. A second conduit transports water vapor to the downstream side of the fan from a chamber above the reservoir.
The device disclosed in U.S. Pat. No. 3,862,819 has several drawbacks. The physical defacement of the oil burner by drilling holes in the fan housing has met with consumer resistance because the oil suppliers claim it affects the mechanical performance of the oil burner. Also, the holes affect oil burner warranties. A more serious drawback is that the liquid level in the reservoir constantly varies and the needle valve arrangement disclosed therein has not been found satisfactory. Depending upon the water level in the reservoir, the pressure will vary. As the water level decreases, it results in more moisture or vapor being introduced into the combustion area, lessening the effectiveness of the combustion for which the system was originally designed. On days of high humidity, it is possible for the water level in the reservoir to exceed the predetermined water level, resulting in a lessening of pressure and decrease in the amount of water vapor introduced into the ignition area, again lessening the efficiency of the combustion.
This constant varying of the water level and therefore the vapor in the chamber results in an uneven metering of the water vapor.
Another drawback is that for different sizes of central heating units, structurally different sizes of orifices for the fuel catalyzers are required.
The present invention is directed to a system for introducing water vapor into a combustion area and the method for operating the same. The invention carefully regulates the metering of water vapor into the combustion area of a heating unit without altering the heating unit structurally. The invention employs only negative pressure (vacuum) and avoids fluctuation in the water level of a reservoir by employing a free floating platform which maintains a constant vapor chamber.
The invention in one embodiment comprises a vacuum-tight housing, a reservoir of water in the housing, and a constant vapor chamber disposed above the reservoir. A vacuum is created in the vapor chamber, which results in an airflow being drawn into the housing and through the reservoir. The airflow entrains metered amounts of highly vaporized water molecules which flow into the vapor chamber and ultimately into the combustion chamber. In a preferred embodiment, a liquid level control system is disposed within the housing to control the liquid level, and the volume of the vapor chamber.
In the preferred embodiment, a vacuum fan is in communication with the power source of the heating unit and provides a secondary airstream. A conduit from the vacuum fan to the housing creates the vacuum for an airflow through the reservoir and the water vapor flows through the conduit, the vacuum fan, and into the combustion zone.